This invention relates to a tire molding apparatus having a tire molding drum the diameter and width of which can be changed.
One example of a conventional tire molding apparatus is as described in the specification of Japanese Patent Application Publication No. 2436/1977. The conventional apparatus comprises: a rotary shaft; a plurality of first drum segments arranged around the front end portion of the rotary shaft, thus forming a cylinder; a plurality of second drum segments arranged around the rear end portion of the rotary shaft, thus forming a cylinder, the second drum segments being paired with the first drum segments, respectively, to form a molding drum; a diameter changing mechanism disposed between the rotary shaft and the first and second drum segments, for transmitting the rotation of the rotary shaft to the first and second drum segments and for moving the first and second drum segments radially to change the diameter of the molding drum; and a plurality of threaded shafts, each having both ends threaded in the opposite directions which are screwed into the first and second drum segments, respectively, the threaded shafts being turned to cause the first and second drum segments to move towards each other or to move away from each other.
The prior art apparatus is disadvantageous in several respects. To change the width of the molding drum, each threaded shaft is turned with a handle to cause the first and second drum segments coupled to the threaded shaft to move towards each other or to move away from each other. Accordingly, the adjusting operation must be carried out as many times as there are of threaded shafts. Accordingly efficiency of the operation is low. Furthermore, as the width of the molding drum is changed by individually adjusting the widths of the first and second drum segments in pairs, in the molding drum the first and second drum segments may provide different widths.